Circuit breaker

ABSTRACT

A circuit breaker includes: at least one external conductor section from an external conductor supply connection in the circuit breaker to an external conductor load connection in the circuit breaker; and a neutral conductor section from a neutral conductor connection in the circuit breaker to a neutral conductor connection in the circuit breaker. The at least one external conductor section includes a mechanical bypass switch and a first mechanical isolating switch which are serially arranged. A second mechanical isolating switch is arranged in the neutral conductor section. A semiconductor circuit arrangement in the circuit breaker is connected in parallel to the bypass switch. A current measuring device is arranged in the at least one external conductor section that is linked to an electronic control unit in the circuit breaker. The electronic control unit operates the bypass switch, the first and second mechanical isolating switches, and the semiconductor circuit arrangement.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2017/072669, filed on Sep. 8,2017, and claims benefit to German Patent Application No. DE 10 2016 117006.2, filed on Sep. 9, 2016. The International Application waspublished in German on Mar. 15, 2018 as WO 2018/046709 under PCT Article21(2).

FIELD

The invention relates to a circuit breaker.

BACKGROUND

A corresponding circuit breaker is known from WO 2015/028634 AI by theapplicant.

Such circuit breakers follow the so-called ‘zero voltage switching’principle.

When the circuit breaker is turned off, first the bypass switch isopened, which results in an electrical arc and the current is commutatedto the semiconductor circuit arrangement.

SUMMARY

In an embodiment, the present invention provides a circuit breaker,comprising: at least one external conductor section from an externalconductor supply connection in the circuit breaker to an externalconductor load connection in the circuit breaker; and a neutralconductor section from a neutral conductor connection in the circuitbreaker to a neutral conductor connection in the circuit breaker,wherein the at least one external conductor section comprises amechanical bypass switch and a first mechanical isolating switch whichare serially arranged, wherein a second mechanical isolating switch isarranged in the neutral conductor section, wherein a semiconductorcircuit arrangement in the circuit breaker is connected in parallel tothe bypass switch, wherein a current measuring device is arranged in theat least one external conductor section that is linked to an electroniccontrol unit in the circuit breaker, wherein the electronic control unitis configured to operate the bypass switch, the first mechanicalisolating switch, the second mechanical isolating switch, and thesemiconductor circuit arrangement as predefined, wherein parallel to thebypass switch, a voltage-dependent resistance is arranged, and whereinthe electronic control unit is configured so that when the circuitbreaker is switched on the electronic control unit operates the secondmechanical isolating switch to close, subsequently to operate the firstmechanical isolating switch to close, and then to switch on thesemiconductor circuit arrangement a predefined first time periodthereafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in even greater detail belowbased on the exemplary figures. The invention is not limited to theexemplary embodiments. Other features and advantages of variousembodiments of the present invention will become apparent by reading thefollowing detailed description with reference to the attached drawingswhich illustrate the following:

FIG. 1 an embodiment of a concrete circuit breaker; and

FIG. 2 a temporal switching sequence of a circuit breaker according toFIG. 1.

DETAILED DESCRIPTION

In an embodiment, the present invention provides a circuit breaker ofthe type mentioned at the beginning with which the disadvantagesmentioned can be avoided, which is a smaller size and a longer servicelife, and which can be manufactured with little effort.

In this way, a circuit breaker can be made that features a small sizeand a long lifespan and can be manufactured with little effort.

In this way, the amplitude of the voltage spike, to which thevoltage-dependent resistance is exposed, is significantly reduced. Inthis way, a voltage-dependent resistance, i.e., a varistor, can be usedwith lower rated voltage. Such a device has a lower leakage current thana varistor with a higher rated voltage, which results in less heating ofthe circuit breaker during operation, which in turn extends the servicelife of this component and the other semiconductors in its vicinity.

In this way, furthermore, lower collector-emitter reverse voltage can beused to equip the semiconductor switches which are usually IGBTs. Inthis way, in addition, diodes with lower periodic peak reverse voltagecan be used. Such modules, compared to modules with higher resilience,have significantly smaller dimensions and are also less costly. In thisway, the costs and the size of a circuit breaker can be lowered and, atthe same time, the heat produced reduced and the corresponding lifespanincreased.

As an alternative here, the electrical durability of a circuit breakercan be significantly increased while the size remains the same.

Semiconductors with a lower collector-emitter reverse voltage orperiodic voltage spikes also have lower internal resistance, which meansthat in the event of a shut-down, the time required to commutate thegrowing short-circuit current by the bypass switch to the firstsemiconductor circuit can be reduced. In this way, the load on thebypass switch and the first semiconductor circuit arrangement can befurther reduced.

By reducing the size, thus the physical surface, of the semiconductor,the loop inductance of the first semiconductor circuit can besignificantly lowered. In addition to the resistance, this is anotherprimary influence factor in the commutation time of the growing shortcircuit current from the bypass branch to the first semiconductorcircuit, which is further lowered by reducing the physical surface areaof the semiconductor.

Furthermore, the higher transient voltage spikes are lowered, which arereleased into the grid through the circuit breaker's internal switchingprocess.

Furthermore, with a snubber in the area of the semiconductor circuitarrangement, it can be significantly reduced or even eliminated.

FIG. 1 depicts a preferred embodiment of a circuit breaker 1 with atleast one external conductor section 2 of an external conductor supplyconnection 3 of the circuit breaker 1 to an external conductor loadconnection 4 in the circuit breaker 1, and a neutral conductor section 5from a neutral conductor connection 6 in the circuit breaker 1 to aneutral load connection 7 in the circuit breaker 1, wherein a mechanicalbypass switch 8 and a first mechanical isolating switch 9 are seriallyarranged in the external conductor section 2, wherein in the neutralconductor section 5, a second mechanical isolating switch 10 isarranged, wherein a semiconductor circuit arrangement 11 in the circuitbreaker 1 is parallel connected to the bypass switch 8, wherein in theexternal conductor section 2 a current measuring device 12 is arrangedthat is connected with an electronic control unit 13 in the circuitbreaker 1, wherein the electronic control unit 13 is designed to operatethe bypass switch 8, the first mechanical isolating switch 9, the secondmechanical isolating switch 10 and the semiconductor circuit arrangement11 in a predefined way, and wherein a voltage-dependent resistance 19 isarranged in parallel to the bypass switch 8, in particular a varistor,wherein the electronic control unit 13 is designed to operate the secondmechanical isolating switch 10 to close only when the circuit breaker 1is switched on, subsequently to operate the first mechanical isolatingswitch 9 to close, and to turn on the semiconductor circuit arrangement11 after a predefined first time period.

In this way, a circuit breaker 1 can be made that has a small size and along lifespan and can be manufactured with little effort.

In this way, the amplitude of the voltage spike, to which thevoltage-dependent resistance 19 is exposed, to be significantly reduced.In this way, a voltage-dependent resistance 19, i.e., a varistor, withlower rated voltage to be used. Such a device has a lower leakagecurrent than a varistor with a higher rated voltage, which results inless heating of the circuit breaker 1 during operation, which in turnextends the service life of this component and the other semiconductorsin its vicinity.

In this way, furthermore, lower collector-emitter reverse voltage can beused to equip the semiconductor switches, which are usually IGBT 21. Inthis way, in addition, diodes with lower periodic peak reverse voltagecan be used. Such modules, compared to modules with higher resilience,have significantly smaller dimensions and are also less costly. In thisway, the costs and the size of a circuit breaker 1 can be lowered whileat the same time the heat produced is reduced and the correspondinglifespan increased. As an alternative, the electrical durability of acircuit breaker 1 can be significantly increased while the size remainsthe same.

Semiconductors with lower collector-emitter reverse voltage or periodicvoltage spikes also show a lower internal resistance which means that inthe event of a shut-down, the time required to commutate the buildingshort-circuit current by the bypass switch to the first semiconductorcircuit 11 can be reduced. In this way, the load on the bypass switch 8and the first semiconductor circuit arrangement 11 can be furtherreduced.

Reducing the size, thus the physical surface, of the semiconductor 21can significantly lower the loop inductance of the first semiconductorcircuit arrangement 11. This is another primary influence factor inaddition to the resistance in the commutation time of the growing shortcircuit power from the bypass branch to the first semiconductor circuitarrangement 11, which is further lowered by the reduction of thephysical surface area of the semiconductor 21.

Furthermore, the higher transient voltage spikes are lowered, which arereleased into the grid through the circuit breaker 1 internal switchingprocess.

Furthermore, with a snubber 24 in the area of the semiconductor circuitarrangement 11, it can be significantly reduced or even eliminated.

The circuit breaker 1 according to FIG. 1 has an external conductorsection 2 as well as a neutral conductor section 5. The externalconductor section 2 runs through the circuit breaker 1 from an externalconductor supply connection 3 to an external conductor load connection4. The neutral conductor section 5 runs through the circuit breaker 1from a neutral conductor connection 6 to a neutral conductor loadconnection 7. The connections 3, 4, 6, 7 are shown as preferably screwterminals or plug connectors, and arranged in the circuit breaker 1 tobe accessible from the outside.

The circuit breaker 1 in question is preferably a low voltagedistribution circuit breaker. The common range is shown as up to 1,000 VAC or 1500 V DC, as is common in the field.

The circuit breaker 1 preferably has an insulated housing.

A mechanical bypass switch 8 and a first mechanical isolating switch 9are serially arranged in the external conductor section 2. A secondmechanical isolating switch 10 is arranged in the neutral conductorsection 5. A semiconductor circuit arrangement 11 is parallel connectedto the bypass switch 8.

Furthermore, parallel-connected to the bypass switch 8 is avoltage-dependent resistor 19 which is, in specific, designed as ametal-oxide varistor.

The circuit breaker 1 furthermore has a current measuring device 12which is arranged in the external conductor section 2 and which ispreferably designed to comprise a shunt resistor.

The current measuring device 12 is connected to an electronic controlunit 13 in the circuit breaker 1 which is preferably designed tocomprise a micro-controller or micro-processor. The electronic controlunit 13 is designed to control the bypass switch 8, the first mechanicalisolating switch 9, the second mechanical isolating switch 10 and thesemiconductor circuit arrangement 11 which is why they are to beoperated or switched as predefined. For this purpose, the electroniccontrol unit 13 is preferably connected circuitry-wise to the firstsemiconductor circuit arrangement 11, as well as further to, inparticular electromagnetic, actuating elements of the mechanicalswitches, therefore the bypass switch 8, the first mechanical isolatingswitch 9 and the second mechanical isolating switch 10. Thecorresponding connections, depending on the electronic control unit 13,are not depicted in FIG. 1.

The semiconductor circuit arrangement 11 preferably comprises arectifier switch 20 which is preferably designed as full bridge, as wellas two power semiconductor switches 21, preferably designed as IGBT, asthe actual switch or regulating elements.

In FIG. 1, the electrical surroundings are indicated next to the actualcircuit breaker 1. It depicts the power supply grid through the AC/DCgrid source 16, the grid interior resistance 17 and the grid inductance18. Furthermore, it depicts an electrical load 23 and an electricalerror 22 in the form of a short circuit.

It is envisioned for a circuit breaker 1 according to FIG. 1 that adisconnection procedure from the bypass switch 8 and the firstsemiconductor circuit arrangement 11 is performed and the first andsecond isolating switches 9, 10 only serve to ensure a galvanicseparation of the load circuit after the disconnection is successful.

For the predefined, in particular manually controlled, disconnecting andswitching-off of the circuit breaker 1, in particular during operationof the circuit breaker 1 within the rated current range, it isenvisioned that the bypass switch 8 is switched off or opened duringzero voltage switching. If the load is reactive, i.e., inductive orcapacitive, the current will not be zero during zero voltage switchingand consequently when it is disconnected. The amount of current is hereknown to be dependent on the related cos (p. It is envisioned that thefirst and second mechanical isolating switches 9, 10 are opened afterthe bypass switch 8 and the subsequent blocking of the IGBT 21, as soonas the current through the circuit breaker 1 is low enough, therefore assoon as the current falls below a pre-settable limit value, especiallyin the area of zero voltage switching for alternating current. Thisallows the heating of the varistor caused by the leakage current to bekept down even with strongly reactive loads.

To switch on the circuit breaker 1, it is envisioned that the electroniccontrol unit 13, which is designed accordingly, first operates thesecond mechanical isolating switch 10 and then the first mechanicalisolating switch 9 so that their switching contacts are closed. Thefirst and second mechanical isolating switches 9, 10 are preferablydesigned as part of a bistable relay. After a predefined first timeperiod, the control unit 13 then activates the semiconductor circuitarrangement 11.

The first time period is preferably long enough that the firstmechanical isolating switch 9 switching contact and the secondmechanical isolating switch 10 switching contact have reached amechanical stationary state. Therefore, they must rest securely againsteach other without bouncing.

The practical implementation of the specific invention has shown thatthe initial time period is between 0.8 ms and 1.2 ms, in particularessentially 1 ms. However, these values may vary depending on the typeof switch for the first and second mechanical isolating switches 9, 10.

The circuit breaker 1 in question is preferably designed for operationboth on a DC grid or on an AC grid.

When the circuit breaker 1 is designed as an AC switch, it is envisionedthat this additionally has a voltage measuring arrangement 29 which isconnected to the control unit 13, and that the electronic control unit13 is designed to operate the first mechanical isolating switch 9 andthe second mechanical isolating switch 10 for a predefined second periodof time before a first zero voltage switching of connected voltage. Thevoltage measurement arrangement 29 is only depicted in FIG. 1 with thecurrent measuring device 12.

Power supply grids with alternating current are generally very stablewith regard to their grid frequency, whereby fluctuations betweendirectly successive zero voltage switchings are extremely low. Thepreferred method is to determine the current period length of therespective grid before the actual switch-on process by means of apredefinable number of zero voltage switchings. This means that such acircuit breaker 1 can be used equally and without further adjustments ingrids with different power line frequencies.

After a few zero voltage switchings, especially eight to twelve, asufficiently accurate value can be determined for the period length. Assoon as this has been done, the determined time period of less than thesecond time period is waited until the first and second mechanicalisolating switches 9, 10 are switched on by the electronic control unit13 after a so-called zeroed zero voltage switching. In this way the twoisolating switches 9, 10 can be switched on at the determined time pointbefore the first zero voltage switching in the sequence shown accordingto which first, the second isolating switch 10, which switches theneutral conductor section 5, is switched on, and only afterwards thefirst isolating switch 9 is closed.

It is preferably envisioned that the second time period is essentiallyhalf the length of the first time period. In doing so, these are thensymmetrically arranged around the first zero voltage switching.

Furthermore, it is preferably envisioned that the electronic controlunit 13 is designed to switch on the bypass switch (8) immediately afterthe first zero voltage switching at a subsequent second zero voltageswitching of connected voltage.

FIG. 2 depicts a corresponding switching procedure in six diagrams 51,52, 53, 54, 55, 56. The first diagram 51 depicts the progression of thevoltage which can be designated as the source voltage. The seconddiagram 52 depicts the logical on-off switching signal of the secondmechanical isolating switch 10, wherein the logical value 1 indicatedwith L, as in diagrams 53, 55 and 56, represents “ON” and the logicalvalue 0 represents “OFF”. The third diagram 53 depicts the logicalon-off switching signal of the first mechanical isolating switch 9. Thefourth diagram 54 depicts the progression of the voltage at thevoltage-dependent resistance 19. The fifth diagram 55 depicts thelogical on-off switching signal for the IGBT. The sixth diagram 56depicts the logical on-off switching signal for the bypass switch 8.

Through the present measures, the semiconductor circuit arrangement 11can also be designed without an attenuator wherein additional componentsare unnecessary and which avoids having to charge a capacitor during theswitch-on process. In this way, the semiconductor circuit arrangement 11uses less current in the switching process. A corresponding attenuator,which is also called a snubber 24, is shown in FIG. 1.

According to the preferred continuation, it is envisioned that thevoltage-dependent resistance 19 is designed as a ThermoFuse varistorwhereby the operation safety can be further increased.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and descriptionare to be considered illustrative or exemplary and not restrictive. Itwill be understood that changes and modifications may be made by thoseof ordinary skill within the scope of the following claims. Inparticular, the present invention covers further embodiments with anycombination of features from different embodiments described above andbelow. Additionally, statements made herein characterizing the inventionrefer to an embodiment of the invention and not necessarily allembodiments.

The terms used in the claims should be construed to have the broadestreasonable interpretation consistent with the foregoing description. Forexample, the use of the article “a” or “the” in introducing an elementshould not be interpreted as being exclusive of a plurality of elements.Likewise, the recitation of “or” should be interpreted as beinginclusive, such that the recitation of “A or B” is not exclusive of “Aand B,” unless it is clear from the context or the foregoing descriptionthat only one of A and B is intended. Further, the recitation of “atleast one of A, B and C” should be interpreted as one or more of a groupof elements consisting of A, B and C, and should not be interpreted asrequiring at least one of each of the listed elements A, B and C,regardless of whether A, B and C are related as categories or otherwise.Moreover, the recitation of “A, B and/or C” or “at least one of A, B orC” should be interpreted as including any singular entity from thelisted elements, e.g., A, any subset from the listed elements, e.g., Aand B, or the entire list of elements A, B and C.

1. A circuit breaker, comprising: at least one external conductorsection from an external conductor supply connection in the circuitbreaker to an external conductor load connection in the circuit breaker;and a neutral conductor section from a neutral conductor connection inthe circuit breaker to a neutral conductor connection in the circuitbreaker, wherein the at least one external conductor section comprises amechanical bypass switch and a first mechanical isolating switch whichare serially arranged, wherein a second mechanical isolating switch isarranged in the neutral conductor section, wherein a semiconductorcircuit arrangement in the circuit breaker is connected in parallel tothe bypass switch, wherein a current measuring device is arranged in theat least one external conductor section that is linked to an electroniccontrol unit in the circuit breaker, wherein the electronic control unitis configured to operate the bypass switch, the first mechanicalisolating switch, the second mechanical isolating switch, and thesemiconductor circuit arrangement as predefined, wherein parallel to thebypass switch, a voltage-dependent resistance is arranged, and whereinthe electronic control unit is configured so that when the circuitbreaker is switched on the electronic control unit operates the secondmechanical isolating switch to close, subsequently to operate the firstmechanical isolating switch to close, and then to switch on thesemiconductor circuit arrangement a predefined first time periodthereafter.
 2. The circuit breaker according to claim 1, wherein thefirst time period which is long enough for the switching contact in thefirst mechanical isolating switch and switching contact in the secondmechanical isolating switch to reach a mechanical stationary state. 3.The circuit breaker according to claim 1, wherein the circuit breaker isconfigured as an alternative current switching device comprising avoltage measuring arrangement that is linked to the electronic controlunit, and wherein the electronic control unit is configured to operatethe first mechanical isolating switch and the second mechanicalisolating switch for a predefined second time period before the firstzero voltage switching of connected voltage.
 4. The circuit breakeraccording to claim 3, wherein the second time period is essentially halfthe length of the first time period.
 5. The circuit breaker according toclaim 1, wherein the first time period is between 0.8 ms and 1.2 ms. 6.The circuit breaker according to claim 3, wherein the electronic controlunit is configured to switch on the bypass switch immediately after thefirst zero voltage switching at a subsequent second zero voltageswitching of connected voltage.
 7. The circuit breaker according toclaim 9, wherein the varistor comprises a ThermoFuse varistor.
 8. Thecircuit breaker according to claim 1, wherein the semiconductor circuitarrangement is configured without an attenuator.
 9. The circuit breakeraccording to claim 1, wherein the voltage-dependent resistance comprisesa varistor.
 10. The circuit breaker according to claim 1, wherein thefirst time period is essentially 1 ms.